Updating an existing extension to use Native Messaging

I currently have an extension (Windows only) that uses ctypes to communicate with external code. I am porting it to use Native Messaging in the new WebExtension API. The update will require installing the manifest file for the messaging application to a specific directory (relative to an already installed application). I will also need to add a registry key to direct Firefox to the manifest file.

My existing extension is on AMO. Is there any way that I can publish a new version on AMO that can do the required installation to get Native Messaging to work on the user’s machine?

Note: This is an extension with very limited applicability. It supports a specific application. We also have a Chrome extension that uses this mechanism, so the messaging application is already installed. We just need to add a manifest file and registry setting that Firefox can understand.

WebExtension add-ons don’t have the ability to install software. One thing you could do is have an update of the legacy add-on install the software, so it’s present once the add-on is updated to the WebExtensions version.